That is a very drastic slippery slope fallacy. You're claiming that if convicted criminals have rights, then crime will take over and run the country. You are incorrectly conflating the preservation of rights with the removal of deterrents.

By the way, which South American countries are communist? If you are thinking of Cuba (which is not South American), then they actually use the criminal justice system to suppress rights, which is what this thread is claiming will happen if the rights of the convicted are removed.

There are so many other problems at the root of stuff like this too.

First question is why do people actually turn to the gangs in the first place? Usually its because the government/society isn't providing something those people need to survive, and the gang does. Either money or community, typically.